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From "Harsh J (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2845) Default replication level mapred.submit.replication=10 causes warnings on small clusters
Date Sat, 03 Sep 2011 19:53:11 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13096751#comment-13096751
] 

Harsh J commented on MAPREDUCE-2845:
------------------------------------

The property 'mapred.submit.replication' is configurable for that reason; or is this a request
to lower that value?

Indeed, this would also hamper decommissioning efforts when an admin doesn't know about it.

I think making it dynamic makes sense, but adds RPC overheads possibly, per submission.

> Default replication level mapred.submit.replication=10 causes warnings on small clusters
> ----------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2845
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2845
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: client, distributed-cache
>    Affects Versions: 0.20.1
>         Environment: Cloudera CDH 2 (hadoop-0.20 0.20.1+169.127-1~lenny-cdh2)
>            Reporter: Christoph Schmitz
>            Priority: Minor
>
> By default, the replication level for job jars, libjars and the distributed cache in
general is mapred.submit.replication=10. This yields under-replication warnings for these
files on small clusters (less than 10 data nodes) when using fsck ("hadoop fsck") on their
HDFS.
> Example on an 8-node cluster:
> {quote}
> /tmp/hadoop/mapred/system/job_201105191458_1857/job.jar:  Under replicated blk_-6996370258385460742_366223.
Target Replicas is 10 but found 8 replica(s).
> {quote}

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